The present invention generally relates to transfer data storage systems, and more particularly to a transfer data storage system which receives a transfer data in which a plurality of kinds of data having arbitrary data lengths are allocated within each frame, extracts the data by the kind of data from the transfer data amounting to a prescribed number of frames, and successively stores the extracted data into a memory.
FIG. 1 shows an example of a transfer data of a subscriber line, where a plurality of kinds of data having arbitrary data lengths are allocated within each frame. This transfer data has one frame formed from a unit of 8 kb/s, and 16 subscriber data are allocated within prescribed positions and transferred within one frame. The 16 subscriber data respectively have arbitrary data lengths depending on the subscriber. In a communication processing system, such a transfer data is multiplexed for every 400 b/s (2.5 ms), for example, with a unit of 20 frames. As shown in FIG. 2, the 16 subscriber data included in the transfer data amounting to 20 multiplexed frames are written into a random access memory (RAM) in the communication processing system for each subscriber.
In FIG. 1, S'ni represents starting position information of an nth subscriber data within the transfer data, and E'ni represents end position information of the nth subscriber data, where i=1, . . . , 20. In addition, 20.times.Sn in FIG. 2 represents storage start address information of the nth subscriber data, and 20.times.En represents storage end address information of the nth subscriber data, where n=1, . . . , 16. The starting position information S'ni and the end position information E'ni of the nth subscriber data are defined from the start of the frame, and thus, the position information may take the same value for different frames i. For this reason, the start and end position information will hereinafter be denoted by S'n and E'n, respectively. On the other hand, the same subscriber data has the same data length within the 20 frames, and the following relationship stands. EQU (20En-20Sn)/20=En-Sn=E'n-S'n
Conventionally, when carrying out the process of converting the above described frame format, a number of RAMs amounting to the number of subscribers are provided, and each subscriber data within the received transfer data is stored independently into the corresponding one of the RAMs. The frame format conversion is realized by successively reading the subscriber data stored in the RAMs, and a speed conversion is made by successively storing the read subscriber data into different RAMs.
However, according to the conventional method described above, there is a problem in that a large hardware is required to make the data transfer. In addition, because the data lengths of the subscriber data within the transfer data are set arbitrarily and the sequence of the subscriber data is also set arbitrarily, there is a problem in that the control of the write operations of the RAMs becomes complex.